Originally Published: 03 JAN 22 14:34 ET

By Omar Jimenez and Elizabeth Stuart, CNN

(CNN) -- The Chicago Teachers Union is planning to convene an emergency meeting to vote on whether its teachers should move to virtual teaching amid a surge in Covid-19 cases, according to a union official, setting up a potential "electronic lockout" by the school district.

Chicago Public Schools, the third-largest school district in the country, resumed in-person learning Monday and has maintained conditions are safe for in-person instruction.

The union meeting, scheduled for Tuesday, would include a poll of the group's delegates (elected union leaders for individual schools) on if they support a return to remote learning until the pandemic is under better control.

The union will also be sending the same question electronically to its roughly 25,000 rank-and-file members Tuesday, according to the official.

If rank-and-file members vote to return to remote learning, those teachers would notify their respective principals either Tuesday evening or Wednesday morning that they would be ready to teach, but only remotely -- effectively walking out of their physical classrooms.

At that point, it would be in the hands of Chicago Public Schools to potentially lock teachers out of their remote classrooms, as the district has threatened to do under similar circumstances in the past.

At a union virtual town hall meeting Sunday, about 80% of the 8,000 members who attended indicated they did not want to return to work in-person under the current conditions, according to the union official.

The vote could trigger a "mass electronic lockout," the official said.

Part of the union hesitation to return has come from a recent surge in Covid-19 cases among both students and in the wider community, along with uncertainty over the current picture of infection.

According to data released by Chicago Public Schools, 35,590 Covid-19 tests were completed by students and staff between December 26 and January 1, and 24,843 were declared invalid. Of those tests that were accepted, 18% tested positive for Covid-19.

In a statement to CNN, Chicago Public Schools wrote, "Over the holiday weekend, we learned from our vendors, ThermoFisher and Color, that more than half of the 40,000 submitted tests could not be validated. While we continue to seek answers, we are focused on increasing on-site testing opportunities for the impacted students and schools this week as part of our ongoing weekly testing."

School system 'deeply concerned'

"CPS is aware of the CTU's calls for possible member actions, including refusal to report to work which CPS is deeply concerned could place the health and safety of members of our community, particularly our students, at increased risk," part of the statement read.

"In the face of evolving pandemic challenges, our plan is to double down on those proven COVID-19 mitigation strategies: vaccination, testing, contact tracing, universal masking; social distancing; strong hand hygiene and respiratory etiquette; monitored and high indoor air quality; appropriately cleaned and disinfected spaces; and making certain staff and families know that sick people must stay home," it continued.

As the school district headed into winter break, it reported its highest weekly Covid-19 case count since the school year began. Citywide, over the past two weeks, Chicago has reported its highest daily case counts of Covid-19 since the start of the pandemic.

"Remote two-way live online instruction" is available for any students directed to quarantine because of coronavirus concerns.